Autonomous Motility of Active Filaments due to Spontaneous Flow-Symmetry Breaking

TL;DR

This paper models how active elastic filaments spontaneously break flow symmetry, leading to autonomous translational or rotational motion, with potential applications in biological and synthetic systems converting chemical to mechanical energy.

Contribution

It introduces a simulation of active filament hydrodynamics showing spontaneous flow symmetry breaking and resulting autonomous motion, a novel insight into active matter behavior.

Findings

Flow symmetry breaking causes autonomous filament motion.

High activity induces nonlinear fluctuating states.

Motion can be translational or rotational depending on symmetry.

Abstract

We simulate the nonlocal Stokesian hydrodynamics of an elastic filament which is active due a permanent distribution of stresslets along its contour. A bending instability of an initially straight filament spontaneously breaks flow symmetry and leads to autonomous filament motion which, depending on conformational symmetry, can be translational or rotational. At high ratios of activity to elasticity, the linear instability develops into nonlinear fluctuating states with large amplitude deformations. The dynamics of these states can be qualitatively understood as a superposition of translational and rotational motion associated with filament conformational modes of opposite symmetry. Our results can be tested in molecular-motor filament mixtures, synthetic chains of autocatalytic particles, or other linearly connected systems where chemical energy is converted to mechanical energy in a fluid environment.